Borehole clamping systems and methods of operating the same

ABSTRACT

A borehole clamping system is provided. The borehole clamping system includes: (a) a pressure actuated clamp for clamping a sensor assembly in a borehole; (b) a fluid control unit configured for use within the borehole, the fluid control unit providing a fluid to the pressure actuated clamp, and controlling a pressure of the fluid; and (c) a surface electrical control unit for controlling flow of the fluid.

RELATED APPLICATION

The present application claims the benefit of priority to U.S.Provisional Patent Application Ser. No. 62/024,044, filed on Jul. 14,2014, the content of which is incorporated in this application byreference.

TECHNICAL FIELD

This invention relates generally to the field of sensing systems, andmore particularly, to improved transducers, accelerometers, and improvedsensing systems.

BACKGROUND OF THE INVENTION

Clamping mechanisms are required to ensure that seismic monitoring tools(such as accelerometers and geophones) that are used for oil, gas andgeothermal energy monitoring applications are well coupled,mechanically, to a borehole. The terms “borehole” and “wellbore” areused herein interchangeably Traditional clamps include: mechanicalbow-spring, motor-driven arms, fixed magnet, and pneumatically-drivenarms.

Existing clamping methods suffer from limitations, such as: (1) highfriction (i.e., drag) throughout the installation/retrieval whichincreases loads on cables and lifting hardware (e.g., crane, workoverrig, etc.), and exacerbates cable torque due to constant resistance totwist at the casing; (2) high temperature limitations of electronics,for example, to 150° C. and less over extended periods of time; and (3)tangling of ancillary control lines (e.g., pneumatic lines) along thelead cable on structures such as blowout preventers, potentiallyresulting in control line damage.

Thus, it would be desirable to provide improved borehole clampingsystems to address these and other issues.

BRIEF SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present invention, aborehole clamping system is provided. The borehole clamping systemincludes: (a) a pressure actuated clamp (e.g., a hydraulically activatedclamp) for clamping a sensor assembly in a borehole; (b) a fluid controlunit (e.g., a hydraulic control unit, such as a hydraulic controlmodule) configured for use within the borehole, the fluid control unitproviding a fluid to the pressure actuated clamp, and controlling apressure of the fluid; and (c) a surface electrical control unit (e.g.,surface electronics 106 shown in FIG. 1) for controlling flow of thefluid, for example, through the operation of one or more valves (e.g.,such as solenoid valves).

According to another exemplary embodiment of the present invention, amethod of operating a clamping system within a borehole is provided. Themethod includes: (a) providing a pressure actuated clamp for clamping asensor assembly in a borehole; (b) providing a fluid to the pressureactuated clamp, and controlling a pressure of the fluid, via a fluidcontrol unit included within the borehole; and (c) controlling, via asurface electrical control unit, flow of the fluid from the fluidcontrol unit to the pressure actuated clamp.

According to yet another exemplary embodiment of the present invention,a borehole clamping system is provided. The borehole clamping systemincludes a pressure actuated clamp (e.g., a hydraulically activatedclamp) for clamping a sensor assembly in a borehole, the pressureactuated clamp configured to be operated using wellbore (i.e., borehole)pressure.

According to yet another exemplary embodiment of the present invention,a method of operating a clamping system within a borehole is provided.The method includes: (a) providing a pressure actuated clamp forclamping a sensor assembly in a borehole; and (b) operating the pressureactuated clamp via wellbore pressure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawings. It is emphasizedthat, according to common practice, the various features of the drawingsare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity purposes.Included in the drawings are the following figures:

FIG. 1 is a block diagram of a borehole clamping system in accordancewith an exemplary embodiment of the present invention;

FIG. 2 is a perspective view of a fluid control unit of a boreholeclamping system in accordance with an exemplary embodiment of thepresent invention;

FIGS. 3A-3B are block diagram views of a sensing assembly of a boreholeclamping system in accordance with an exemplary embodiment of thepresent invention; and

FIGS. 4 is a block diagram schematic illustrating fluid flow of aborehole clamping system in accordance with an exemplary embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to certain exemplary embodiments, the present inventionrelates to passive energizing and release of clamps arms included insensor assemblies. Only increased ambient (e.g., wellbore or borehole)pressure is used. Motors, pumps or other motive force producers may beavoided through the use of ambient pressure increased using a pressureconverter. Because motors, pumps, etc. are avoided in the clampingoperations, standard hybrid (e.g., electrical/optical) cable may be usedto control the clamping action. Thus, ancillary lines (e.g., carryinghydraulic fluid) to the surface may be avoided in the lead cable.Rather, such ancillary lines may be included in the short lengths ofinterconnect cable. In certain exemplary embodiments of the presentinvention, passive electronics may be utilized that are typicallyreliable at temperatures above 200° C. including solenoid valves. Checkvalves may be utilized to ensure that clamps remain released duringinstallation, when large excursions of pressure and temperature areexperienced by the system.

Referring now to the drawings, FIG. 1 illustrates a borehole clampingsystem 100 installed in connection with a borehole 104. That is, aborehole (i.e., a wellbore) 104 is formed in earth 102. Sensorassemblies 112 a, 112 b, . . . , 112 n (e.g., where the sensorassemblies may be provided in an array such as the illustrated sensorassembly string including assemblies 112 a, . . . , 112 n) are loweredinto borehole 104 to sense vibration information within borehole 104. Ina specific example, borehole 104 may be provided in connection with gasand oil exploration, reservoir monitoring and production monitoringactivities, and sensor assemblies 112 a, 112 b, . . . , 112 n includesensors for sensing information related to such activities. Such sensorsmay be fiber optic sensors (e.g., fiber optic transducers, fiber opticaccelerometers, etc.), electronic sensors, etc.

Each of the sensor assemblies is desirably securely positioned withinborehole 104. For example, sensor assembly 112 a includes a clamp arm112 a 1 (e.g., a pressure actuated clamp) for securely pressing sensorassembly 112 a against a wall (e.g., a casing wall) 104 a of borehole104. The remaining sensor assemblies (e.g., sensor assembly 112 nincluding clamp arm 112 n 1) are also securely positioned withinborehole 104.

In the example shown in FIG. 1, system 100 also includes surfaceelectronics 106 (e.g., interrogation electronics for interrogatingsensors in sensor assemblies 112 a, . . . , 112 n and hydrauliccontrol/monitoring electronics), lead cable 108, fluid control unit 110(e.g., a hydraulic fluid control unit for operating and controllinghydraulically actuated clamps 112 a 1, . . . , 112 n 1, etc.), andinterconnect cables 114. In an exemplary application including fiberoptic sensing of the sensor assemblies, lead cable 108 may includeoptical fibers for sending and receiving optical signals to fiber opticsensors within the sensor assemblies 112 a, . . . , 112 n 1. Lead cable108 may also include, for example, electrical conductors, etc. forperforming operations in connection with fluid control unit 110 (e.g.,operating solenoid valves in fluid control unit 110). Depending on theapplication, interconnect cables 114 may carry, for example, fiber opticsignals, hydraulic fluid, etc.

FIG. 2 illustrates an example of fluid control unit 110 from FIG. 1. Incertain exemplary embodiments of the present invention, fluid controlunit 110 may be a hydraulic fluid control unit for controlling hydraulicfluid used to operate the various sensor assembly clamps. FIG. 2illustrates an end of lead cable 108 entering into cable shroud 110 e 1of control unit 110. Control unit 110 also includes a pressure reliefmodule 110 c (including pressure relief valves 110 c 1, 110 c 2, and oneor more electronic or optical fiber pressure transducers 116 formonitoring fluid pressure at one or more locations shown in FIG. 4), asolenoid valve manifold 110 d (including solenoid control valves 110 d1, 110 d 2, 110 d 3 and hydraulic lines to control the flow of hydraulicfluid for clamping and release functions), a pressure converter (e.g., apressure intensifier) 110 a, an isolation device 110 b, and anothercable shroud 110 e 2 leading to interconnect cable 114. Exemplaryfunctions of certain of the elements of control unit 110 are explainedbelow in connection with the example shown in FIG. 4.

FIGS. 3A-3B illustrate an exemplary operation of clamp 112 a 1 of sensorassembly 112 a (in an exemplary embodiment of the present inventionwhere clamp 112 a 1 of sensor assembly 112 a is hydaulically actuatedand controlled). Referring specifically to FIG. 3A, sensor assembly 112a is securely positioned in borehole 104 such that feet 112 d ofassembly 112 a are pressed against one wall 104 a of borehole 104, andclamp arm 112 a 1 is pressed against another wall 104 a of borehole 104.Fluid 116 a (e.g., an incompressible fluid, such as an incompressiblehydraulic fluid) is injected through a hydraulic line into cylinder 112e on the left side of piston 112 f (and fluid 116 b is likewise forcedout on the right side of piston 1120. The addition of fluid 116 acreates a positive differential across piston 112 f, and therefore movespiston 112 f to the right, compressing spring 112 h and driving pistonrod 112 g to the right, thereby actuating clamp arm 112 a 1 (which iscoupled and/or linked to piston rod 112 g), and pressing clamp arm 112 a1 against wall 104 a as shown in FIG. 3A. In this position, the sensingto be done by sensor 112 c (e.g., a fiber optic sensor including a fiberoptic transducer and/or fiber optic accelerometer) included in sensorassembly 112 a may be accomplished in connection with surfaceelectronics 106.

After the sensing is complete, and sensor assembly 112 a is to bewithdrawn from borehole 104 (e.g., along with other sensor assemblies inan array), the situation in FIG. 3B occurs. That is, fluid 116 b (e.g.,an incompressible fluid) is injected into cylinder 112 e on the rightside of piston 112 f (and fluid 116 a is likewise forced out on the leftside of piston 112 f, for example, to substantially equalize fluidpressure on each side of cylinder 112 e and likewise across piston 112f), allowing spring 112 h to naturally extend, thereby pushing piston112 f to the left and pulling piston rod 112 g to the left, therebyretracting clamp arm 112 a 1 such that clamp arm 112 a 1 does not pressagainst wall 104 a. With clamp arm 112 a 1 in the retracted positionshown in FIG. 3B, sensor assembly 112 a may be withdrawn from borehole104. While sensor assembly 112 a is shown in FIGS. 3A-3B alone inborehole 104, it is understood that sensor assembly 112 a may be part ofa sensor array including a plurality of sensor assemblies, such as isshown in FIG. 1.

FIGS. 4 is a block diagram fluid schematic of an exemplary configurationof fluid control unit 110 in a hydraulic fluid control configuration.Also shown are simplified sensors assemblies 112 a, 112 b, . . . , 112 n(shown in more detail in FIGS. 3A-3B) included in borehole clampingsystem 100 (see FIG. 1). In the example shown in FIG. 4, fluid controlunit 110 includes a pressure converter 110 a (e.g., a pressureintensifier) for operating the clamp arms of sensor assemblies 112 a,112 b, . . . , 112 n, where pressure converter 110 a includes piston 110a 1 within cylinder 110 a 2. In the example shown in FIG. 4, pressureconverter 110 a (intensifier) includes two coupled dissimilar diametercylinder/piston assemblies for creating a higher pressure outputcompared to an input pressure.

Unit 110 also includes an isolation device 110 b (e.g., a device forisolating the active fluid for driving pistons, such as piston 112 f,from wellbore fluid, such as a mud piston system, etc.) having a piston110 b 1 in a cylinder 110 b 2. Cylinder 110 b 2 of isolation device 110b separates borehole fluid (at wellbore pressure) from working (clean)fluid with no pressure difference and serves as a reservoir toaccommodate changes in overall system fluid volume. Unit 110 alsoincludes: pressure relief valves 110 c 1, 100 c 2; check valves 110 c 3,110 c 4; and solenoid valves 110 d 1, 110 d 2, and 110 d 3 (controlledby surface electronics 106).

During installation of the sensor assemblies 112 a, 112 b, . . . , 112 ninto borehole 104, the hydraulics may be considered to be at surfaceambient pressure. Solenoid operated valves 110 d 1, 110 d 2, and 110 d 3are closed (e.g., using surface electronics 106), such that the clamparms 112 a 1, etc. are in a retracted position for lowering intoborehole 104. During the installation, check valves 110 c 3, 110 c 4desirably ensure that both sides of clamp pistons (e.g., such as piston112 f shown in FIGS. 3A-3B) are at approximately wellbore pressure.

After the sensor assemblies are lowered into borehole 104, the wellborepressure increases with hydrostatic pressure (or applied pressure, orboth), resulting in an increase (amplification) in the pressure on thehigh pressure side (with the smaller piston/cylinder diameter) ofpressure converter 110 a (e.g., a pressure intensifier). With solenoidvalves 110 d 1 and 110 d 3 now in an open position (controlled usingelectrical signals from surface electronics 106), the resulting fluidmovement causes the clamping pistons (e.g., piston 112 f shown in FIGS.3A-3B) to drive the clamp arms (e.g., clamp arm 112 a 1) into anextended position (e.g., through the piston rods such as rod 112 g),such as the position shown in FIG. 3A. Solenoid valves 110 d 1 and 110 d3 are then closed electrically (controlled using electrical signals fromsurface electronics 106) to ensure that the clamp arms remain extendedfor long periods of time.

In order to release the clamp arms, solenoid valve 110 d 1 is closed(via electrical signals from surface electronics 106), and solenoidvalves 110 d 2 and 110 d 3 are in an open position. In thisconfiguration, both sides of clamp pistons (e.g., piston 112 f shown inFIGS. 3A-3B) have substantially equal pressure (i.e., wellborepressure). A mechanical spring force from spring 112 h is used toretract the clamp aims, for example, as shown in FIG. 3B.

In order to retrieve the sensor assemblies from borehole 104, each ofsolenoid valves 100 d 1, 110 d 2, and 110 d 3 are then closed. The wellpressure decreases with depth as the sensor assemblies are lifted to areduced depth. A positive pressure across the clamp pistons (e.g.,piston 112 f shown in FIGS. 3A-3B) works with the retraction springs(e.g., spring 112 h in FIGS. 3A-3B). The pressure relief valve onrelease side is set to a slightly higher cracking pressure than thecheck valve on the clamping side, thereby providing a slightly higherpressure on the release side of the clamps throughout the entireretrieval to ensure that the clamps remain released.

The sensing assemblies/tools described herein may include, for example,tools for sensing mechanical and/or acoustic vibration . Such tools mayinclude electronic sensing elements (e.g., geophones), fiber opticsensing elements, among others. Exemplary fiber optic sensing elementsinclude fiber optic transducers and accelerometers. Exemplary fiberoptic transducers and accelerometers are disclosed in U.S. PatentApplication Publication No. 2012/0257208, titled “FIBER OPTICTRANSDUCERS, FIBER OPTIC ACCELEROMETERS AND FIBER OPTIC SENSINGSYSTEMS”, which is hereby incorporated by reference in its entirety.

Exemplary applications for the sensing assemblies/tools (e.g.,electronic sensing elements, fiber optic sensing elements, etc.) includevertical seismic profiling (VSP), three dimensional sub-surface mapping,microseismic monitoring, machine vibration monitoring, civil structure(e.g., dams, bridges, levees, etc.) monitoring, tunnel detection,perimeter/border security, earthquake monitoring, borehole leakdetection, amongst others.

Although illustrated and described above with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the spirit of the invention.

What is claimed:
 1. A borehole clamping system comprising: a pressureactuated clamp for clamping a sensor assembly in a borehole; a fluidcontrol unit configured for use within the borehole, the fluid controlunit providing a fluid to the pressure actuated clamp, and controlling apressure of the fluid; a surface electrical control unit for controllingflow of the fluid.
 2. The borehole clamping system of claim 1 whereinthe fluid is an incompressible fluid.
 3. The borehole clamping system ofclaim 1 wherein the fluid is a hydraulic fluid.
 4. The borehole clampingsystem of claim 1 wherein the surface electrical control unit controlsflow of the fluid through the operation of one or more valves includedin the fluid control unit.
 5. The borehole clamping system of claim 1wherein pressure used to operate the pressure actuated clamp is providedvia wellbore pressure.
 6. The borehole clamping system of claim 1wherein the fluid control unit includes a pressure converter forincreasing a pressure used to actuate the pressure actuated clamp.
 7. Amethod of operating a clamping system within a borehole, the methodcomprising the steps of: (a) providing a pressure actuated clamp forclamping a sensor assembly in a borehole; (b) providing a fluid to thepressure actuated clamp, and controlling a pressure of the fluid, via afluid control unit included within the borehole; and (c) controlling,via a surface electrical control unit, flow of the fluid from the fluidcontrol unit to the pressure actuated clamp.
 8. The method of claim 7wherein the surface electrical control unit controls flow of the fluidfrom the fluid control unit to the pressure actuated clamp through theoperation of one or more valves included in the fluid control unit. 9.The method of claim 7 wherein pressure used to operate the pressureactuated clamp is provided via wellbore pressure.
 10. The method ofclaim 7 wherein the fluid control unit includes a pressure converter forincreasing a pressure used to actuate the pressure actuated clamp.
 11. Aborehole clamping system comprising: a pressure actuated clamp forclamping a sensor assembly in a borehole, the pressure actuated clampconfigured to be operated using wellbore pressure.
 12. The boreholeclamping system of claim 11 further comprising a fluid control unitconfigured for use within the borehole, the fluid control unit providinga fluid to the pressure actuated clamp, and controlling a pressure ofthe fluid.
 13. The borehole clamping system of claim 12 wherein thefluid control unit includes a pressure converter for increasing apressure used to actuate the pressure actuated clamp.
 14. The boreholeclamping system of claim 12 further comprising a surface electricalcontrol unit for controlling flow of the fluid.
 15. The boreholeclamping system of claim 14 wherein the surface electrical control unitcontrols flow of the fluid through the operation of one or more valvesincluded in the fluid control unit.
 16. The borehole clamping system ofclaim 12 wherein the fluid is an incompressible fluid.
 17. The boreholeclamping system of claim 12 wherein the fluid is a hydraulic fluid. 18.A method of operating a clamping system within a borehole, the methodcomprising the steps of: (a) providing a pressure actuated clamp forclamping a sensor assembly in a borehole; and (b) operating the pressureactuated clamp via wellbore pressure.
 19. The method of claim 18 furthercomprising the step of providing a fluid to the pressure actuated clamp,and controlling a pressure of the fluid, via a fluid control unitincluded within the borehole.
 20. The method of claim 19 furthercomprising the step of controlling, via a surface electrical controlunit, flow of the fluid from the fluid control unit to the pressureactuated clamp.
 21. The method of claim 20 wherein the surfaceelectrical control unit controls flow of the fluid from the fluidcontrol unit to the pressure actuated clamp through the operation of oneor more valves included in the fluid control unit.
 22. The method ofclaim 19 wherein the fluid control unit includes a pressure converterfor increasing a pressure used to actuate the pressure actuated clamp.